Synaesthesia, where specific stimuli automatically trigger additional perceptual experiences, offers insight into conscious perception. While traditionally considered congenital, growing evidence shows that synaesthesia-like experiences can be induced in non-synaesthetes, even in adulthood. This review examines various methods for artificially inducing such experiences and compares them to natural synaesthesia's hallmarks: consistency, automaticity, and lack of 'perceptual presence'. The authors conclude that many aspects of synaesthesia can be induced, suggesting developmental and learning components in its acquisition and extending evidence of perceptual plasticity in adults.
Exposure to rapid, bright stroboscopic light has been known for over 200 years to induce vivid visual hallucinations of color and geometric shapes. This narrative review summarizes the history of research on stroboscopic light stimulation (SLS), its recreational and lay-therapeutic uses, the phenomenology of the experiences it produces, and current understanding of potential neural mechanisms. Despite progress, fundamental questions remain about the full characterization of its phenomenology, its precise physiological origins, the conditions under which it leads to altered states of consciousness, and possible clinical applications.